<?php
class Application_Service_User
{
	private static $_instance = NULL;
	
    private function __construct () {}
    
    private function __clone() {}
    
    public static function getInstance() {
    	if(self::$_instance == NULL) {
    		self::$_instance = new self();
    	}
    	return self::$_instance;
    }
    
    public function login($username, $password) {
    	
    }
    
    public function logout() {
    	
    }
}
?>